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allophane

Phyllosilicate mineral or mineraloid

Instance of: mineral species
1
Sources
1.Stated in The IMA List of Minerals (July 2019)
View statement on Wikidata ↗
Subclass of: solid geologic material

Overview

From Wikipedia, the free encyclopedia · Read full article · Text CC BY-SA 4.0

Allophane is an amorphous to poorly crystalline hydrous aluminium silicate clay mineraloid. Its chemical formula is Al2O3·(SiO2)1.3-2·(2.5-3)H2O. Since it has short-range atomic order, it is a mineraloid, rather than a mineral, and can be identified by its distinctive infrared spectrum and its X-ray diffraction pattern. It was first described in 1816 in Gräfenthal, Thuringia, Germany. Allophane is a weathering or hydrothermal alteration product of volcanic glass and feldspars and sometimes has a composition similar to kaolinite but generally has a molar ratio of Al:Si = 2. It typically forms under mildly acidic to neutral pH (5–7). Its structure has been debated, but it is similar to clay minerals and is composed of curved alumina octahedral and silica tetrahedral layers. Transmission electron micrographs show that it is generally made up of aggregates of hollow spherules ~3–5 nm in diameter. Allophane can alter to form halloysite under resilicating aqueous conditions and can alter to form gibbsite under desilicating conditions. A copper-containing variety cupro-allophane has been reported.

Overview

All data

33 statements · 33% with external sources · numbers in brackets are citations

Nickel-Strunz 9th edition (updated 2009): 9.ED.20
IMA status and/or rank: grandfathered mineral (G)
1
Sources
1.Stated in IMA/CNMNC List of Mineral Names (March 2007)
View statement on Wikidata ↗
Nickel-Strunz '10th ed', review of (9th ed/ 2009 update): 9.ED.20
1
Sources
1.Stated in MinDat
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Streak color: white
Named after: visual appearance language: Ancient Greek · object of statement named as: φαίνεσθαι "phainesthai"
1
Sources
1.Stated in A Dictionary of the Names of Minerals
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other language: Ancient Greek · object of statement named as: ἄλλος "allos"
1
Sources
1.Stated in A Dictionary of the Names of Minerals
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IMA Mineral Symbol: Alp
1
Sources
1.Stated in IMA–CNMNC approved mineral symbols
View statement on Wikidata ↗
Formula: Al₂O₃(SiO₂)₁.₃-₂.₀·2.5-3.0H₂O
1
Sources
1.Stated in The IMA List of Minerals (December 2014)
View statement on Wikidata ↗
Strunz 8th edition (series ID, updated): VIII/E.11 – Anhang
1
Sources
1.Stated in Mineralogische Tabellen : Eine Klassifizierung der Mineralien auf kristallchemischer Grundlage, mit einer Einfuhrung in die Kristallchemie (1982)
View statement on Wikidata ↗
Mohs' hardness: 3

On other databases

18 identifiers linking allophane across the web's reference databases

Data quality

statements

33%

externally sourced

Source last edited October 30, 2026. AIDb refreshes this page daily.

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AIDb. (2026). allophane (Q429712). Retrieved from https://aidb.si/e/allophane-Q429712